Stratum corneum chymotryptic enzyme (SCCE) is a member of the kallikrein family of serine proteases. Hansson L. et al. (1994; J. Biol. Chem. 269: 19420-19426) cloned the SCCE gene and showed that it is expressed specifically in the outermost layer of the epidermis, known as the stratum comeum. SCCE is likely to function in proteolysis of intercellular cohesive structures. Such proteolysis is necessary for desquamation, the ongoing process by which outer layers of skin are eliminated. An imbalance in desquamation and new epidermis growth may lead to the formation of scales on the skin surface, a common occurrence in diseases such as psoriasis and icthyosis.
Genes encoding the three human kallikreins, tissue kallikrein (KLK1), glandular kallikrein (KLK2), and PSA are located in a cluster at chromosome map position 19q13.2-q13.4 (Riegmen P. H. (1992) Genomics 14: 6-11). PSA shares more extensive homology with KLK2 than with KLK1. Both PSA and KLK2 are produced by prostate epithelial cells and their expression is regulated by androgens. Three amino acid residues were found to be critical for serine protease activity, residues H.sub.65, D.sub.120, and S.sub.213 in PSA (Bridon D. P. et al. (1995) Urology 45: 801-806). Substrate specificity, described as chymotrypsinogen-like (with KLK2) or trypsin-like (with PSA) is thought to be determined by S.sub.207 in PSA and D.sub.209 in KLK2 (Bridon et al., supra). KLK1 is chymotrypsinogen-like and expressed in the pancreas, urinary system, and sublingual gland. KLK1, like the other kallikreins, is made as a pre-pro-protein and is processed into an active form of 238 amino acids by cleavage of a 24 amino acid terminal signal sequence (Fukushima D. et al. (1985) Biochemistry 24: 8037-8043).
Adenocarcinoma of the prostate accounts for a significant number of malignancies in men over 50, with over 122,000 new cases occurring per year, in the United States alone. Prostate-specific antigen (PSA) is the most sensitive marker available for monitoring cancer progression and response to therapy. Serum PSA is elevated in up to 92% of patients with prostatic carcinoma, depending upon tumor volume.
Discovery of proteins related to SCCE, PSA, and the polynucleotides encoding them satisfies a need in the art by providing new compositions useful in diagnosis, prevention, and treatment of cancer and skin disorders.